1. Field of the Invention
This invention relates generally to a heatable backlight panel, and more particularly, to a plastic composite backlight panel for convertible vehicles.
2. Background Art
The use of heatable window assemblies for removing ice and snow from the windows of aircraft and similar vehicles are well-known in the art.
U.S. Pat. No. 3,020,376 discloses a laminated plastic panel for aircraft that is electrically conductive so as to be kept free of ice and fog formations. In addition to the polyvinyl butyral sheet, the panel includes a sealer layer, an adhesive layer, an electrically conductive layer, a second adhesive layer, and a protective layer. The electrically conductive layer is deposited onto the panel by thermal evaporation methods.
U.S. Pat. No. 3,041,436 involves a transparent, electrically conductive window for aircraft for anti-fogging and de-icing applications. The window consists of an outer face sheet, an interlayer, and an inner ply. The inner side of the face sheet is coated with an electrically conductive coating.
U.S. Pat. No. 3,180,781 relates to a composite laminated structure consisting of two sheets of rigid plastic sandwiched around an interposed layer. The composite structure is primarily used for aircraft to prevent fogging and icing. An unbroken, electrically conductive film is applied to one of the laminated sheets, and may consist of a series of layers placed over each other. The interposed layer consists of a sealing layer, an adhesive layer, a conducting film layer, and a second adhesive layer.
U.S. Pat. No. 3,636,311 discloses a heating device for defrosting or deicing automobile windows. The layer of conductive material is printed or sprayed onto the surface of the polyester resin sheet. A self-adhesive border surrounds the sheet which is used to subsequently attache the sheet to a window or a windscreen.
Removing ice and snow from the flexible plastic backlight panels manually with scrapers and the like, is a problem because of the likelihood that the plastic will be scratched or otherwise damaged. Defrosting the backlight panel with blasts of hot air requires considerable time for the air to heat up in cold weather, and generally results in uneven heat distribution across the backlight panel.
Much of this prior art technology although applicable to automobiles, was developed primarily for the aircraft industry. Hence, the laminates are made of rigid plastic panels to withstand the extreme temperature and pressure differentials normally encountered at extreme flight altitudes.
Although rigid glass panels which may be heated through a plurality of electrical members mounted within the panels have been used in automobiles for many years, this technology has not bee refined for application to the thinner, flexible, plastic panels that are used in convertible tops. What is needed is an inexpensive, rugged, flexible, composite plastic backlight panel that provides an even heat distribution across the entire surface of the panel. The flexibility of the panel is critical because when the backlight panel is in the raised position, the panel will assume a curved configuration so as to enable the designer to provide sleek lines and an aerodynamically efficient design, but must lie flat in the retracted position for efficient storage.